Tandem Copper-Catalyzed Regioselective -Arylation-Aza-Michael Addition: Synthesis of Tetracyclic 5-Benzothiazolo[3,2-]quinazoline Derivatives.

A copper-catalyzed tandem process integrating regioselective -arylation, followed by aza-Michael addition, is disclosed using 2-aminobenzothiazoles and -halo cinnamic acid congeners. This process generated diverse tetracyclic 5-benzothiazolo[3,2-]quinazoline derivatives in moderate to good yields. The present tandem reaction appears to proceed through concomitant ring opening of 2-aminobenzothiazole and -arylation to give the -cyanamide-substituted diaryl thioether intermediate. The thus generated intermediate likely undergoes an unprecedented Truce-Smiles-type rearrangement involving - to -aryl migration, followed by reformation of the thiazole ring and intramolecular aza-Michael addition to furnish the title products.